The use of mobile devices having larger displays is becoming more ubiquitous in devices such as cell phones, hand held games, MP3 players, watches, laptop computers, mobile GPS and other display screens in cars, touch panel screens, and other electronic devices without limitation. At least a portion of the cover plate is transparent, so as to allow the user to view a display. For some applications, the cover plate is sensitive to the user's touch. As the use of such devices increases the probability of the cover glass breaking or suffering damage due to accidents, cleaning negligent use and ordinary use also increases. The presently available cover glasses are not designed or selected to survive the high levels of abuse or some or the ordinary accident that can occur such as sharp contact or impact with another object. Due to frequent contact, such cover plates must have high strength and be scratch resistant.
The “selection criteria” for the existing glasses, though not always a requirement, has typically been limited to the following:                1. A minimum height that the glass will have to survive when a 135 g ball is dropped on the glass that is supported in a prescribed manner;        2. A minimum strength as measured by a four point bend test; and        3. A hardness which although measured is typically not a requirement.These “criteria” for existing protective glass used in display devices are not well understood. Moreover, the primary test method for accepting cover glass as fit-for-use is a ball drop test, a test known to the inventors for its inability to accurately assess damage resistance of glass because it is sensitive to existing surface flaws and not to the introduction of new flaws. Strength testing, for example, immediately after ion exchange, has also been used as a predictor of the protective capability of cover glass. These tests will naturally lead one to value high surface compressive stress over a deep ion exchange layer. The inventors have found that this is incorrect and the opposite is actually true. Consequently, the present thin cover glass in these devices has not been optimized for glass and ion exchange properties that directly relate to abrasion resistance and visual appearance in these devices. For example, current soda lime silicate (“SLS”) glass used in mobile devices is mechanically hindered by inherent limitations in its ion exchange capability.        
The criteria described above has been applied to select glasses that are primarily in the soda-lime silicates family, including version in which the alumina content is elevated—referred to as aluminosilicates or modified-aluminosilicates. [United States Patent Application Publication 2008-0286548 A1 mentioned above discloses some glass compositions that are an improvement over cover glass formulations of the prior art]. We have found that these criteria do not describe actual failure modes observed in the field for these devices. The requirements defined by the prior art does not predict how much load the glass can withstand when the mobile device is dropped on a sharp object such a small stone. It also does not predict how the glass will survive after the mobile device has experienced in-service use with accumulated damage on the surface. The prior art requirements can result in parts with unacceptably poor strength and scratches. The present invention overcomes the difficulties present in glasses currently used as protective covers and/or touch screens in electronic devices.